Why is the ban needed?

Homeland Security officials say terrorists are trying to smuggle explosives onto planes in “various consumer items,” and experts say explosives could be concealed within the electronics and battery compartments of consumer devices. The devices are still allowed to be placed in checked baggage.

What about the threat of items in the cargo hold?

The British Airline Pilots’ Association says it's worried this ban could lead to more accidental fires in cargo holds, posing a greater risk than that of terrorism. Spare lithium batteries are already banned from cargo holds over concerns that they can cause intense, fast-growing fires without being seen belowdecks, and accidental fires cased by lithium batteries have been cited in two crashes, the association said.

Have bombs been concealed in electronic devices before?

Yes. On June 23, 1985, a bomb concealed inside a radio inside a checked bag exploded onboard an Air India flight from Montreal to London while over Irish airspace, killing all 329 people aboard. And Pam Am Flight 103 was blown up by terrorists on Dec. 21, 1988 over Lockerbie, Scotland shortly after takeoff. A bomb concealed inside a tape recorder inside checked luggage brought the plane down, killing 259 people aboard, along with 11 people on the ground.

What about items not concealed in electronic devices?

Terrorists have also tried to smuggle powdered explosives aboard in their clothing, and concerns about liquid explosives led to the restriction of large containers of liquids, aerosols or gels in hand baggage.

What devices does the laptop ban apply to?

The restriction extends to many other devices, including cameras, tablets, e-readers, portable DVD players and electronic game units larger than a smartphone. There’s an exception for medical devices, but those will be subject to extra screening. Cell phones of a “commonly available” size are still allowed onboard.

What airports are affected?

Right now, the ban applies only to U.S.-bound flights from 10 foreign airports. They are:

How many flights does this currently affect?

Homeland Security says it only applies to a “small percentage” of flights entering the United States daily, and the exact number varies. Airlines departing from these airports will know in advance which flights are affected by these measures.

Could this be expanded?

American security officials have been meeting with their European counterparts to discuss the potential for expanding this ban to European airports. An average of 400 nonstop flights leave Europe for the United States daily, or about 105,000 travelers daily.

Travel-industry experts say U.S. officials risk alienating tourists and business travelers if they don’t manage an expansion of the ban smoothly especially because business travelers who expect to be able to work on their laptops account for a high percentage of revenue on those flights.